Safety switch

ABSTRACT

A safety switch includes a switch housing having at least one key channel into which a key can be introduced from the exterior. A plate cam projects into key channel and rotates when the key is introduced. A mechanism in secures the plate cam when the key has been fully introduced or completely removed.

FIELD OF THE INVENTION

The present invention relates to a safety switch having a switch housingwith at least one key passage for receiving a key from exterior of theswitch housing and with a plate cam rotatably mounted in the switchhousing. Upon introduction of the key in the key passage, the keyrotates the plate cam.

BACKGROUND OF THE INVENTION

Safety switches, such as disclosed in DE 44 08 024 A1, serve to make thecurrent supply feeding electrical machinery dependent upon whethercertain protection devices, which are integral with the machine, arepositioned in the correct setting. With some embodiments, the safetyswitch does not connect the control current circuit supplying a currentsupply to the machine because the protection devices have greatertolerances than allowed by the safety switch.

EP-A1-0 707 329 discloses a safety switch with a plate cam mountedrotatably on an axis on which are arranged interlocking means. Theinterlocking means lock or secure the plate cam when the key is notintroduced and are thrust out of their blocking position when the key isintroduced. The plate cam is released with further introduction of thekey, with the interlocking means being rotated together with the platecam.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide an improved safetyswitch in which the plate cam is prevented from rotating as a result ofmachine vibrations when the key is in or out of the key passage.

The foregoing objects are basically obtained by a safety switchcomprising a switch housing, a first key passage in the switch housing,a key receivable in the key passage from a location exterior of theswitch housing, and a plate cam projecting into the key passage androtatable in the switch housing about a rotational axis uponintroduction of the key. Securing means in the switch housing securesthe plate cam against rotation when the key is completely introducedinto the key passage and when the key is completely outside the keypassage. It also allows the key to be introduced deeper into the keypassage after the plate cam is secured by the securing means.

By securing the plate cam when the key is completely inserted, the platecam is prevented from rotating as a result of vibrations of the machineoccurring during key insertion, so that the key can no longer be pulledout. The key is inserted to a certain depth of introduction followingtermination of the rotary displacement of the plate cam. Since thesecuring means allows the plate cam to permit a deeper introduction ofthe key, in other words allowing for a "track alignment arrangement" ofgreater length, even imprecise switch-throwing protection devices can bereliably controlled. In advantageous embodiments, the plate cam issecured even when the key is not inserted.

In one preferred embodiment, the means for securing the plate cam arerealized by the plate cam having at least one recess which cooperateswith a blocking element movable relative to the plate cam.

The recess can be provided, for example, in an additional material partconstructed on the side of the plate cam. The blocking element can bearranged on one side of the plate cam and constructed and shaped inconformation with a movable interlocking member. With this embodiment,parts can be used which are already present in known safety switches.This reduces the number of new required parts and reduces the requiredmodifications of the tools. One especially space-saving embodiment isobtained when the interlocking member can be movable perpendicular tothe rotary axis of the plate cam.

The recess and blocking element can also be realized, for example, insuch a manner that the recess is provided in an area of the plate cam,which with rotation of the plate cam, projects into the key passage.Also the blocking arrangement can be provided as part of the key. Anespecially simple realization of the blocking element is obtained with alongitudinally slotted, fork-shaped key, and formed by recessed cutoutsections provided on the interior of the key slot. The recess is thenconfigured to be groove-like, whereupon the plate cam retains itsfracture and break-resistance. The recess could also penetrate theentire thickness of the plate cam, whereby a material part passing allthe way through the key could be provided, instead of the recessedcutout sections.

The operational capacity of the safety switch is preferably additionallyenhanced in that the securing means are provided for symmetricalsecuring of both sides of the plate cam.

A broadening of the possibilities of utilization of the safety switch ofthe present invention is obtained when this switch has two, non-parallelkey passages, preferably extending perpendicular to one another, intowhich the key can be introduced as desired. Operation members canproject outward into the key passage when the key is not introduced, andpreferably are connected with interlocking members for the securing ofthe plate cam in this setting and disconnect the plate cam uponintroduction of the key. The number of required component parts isreduced in a simple manner, when such operation member can be displacedalong an angle-bisecting line bisecting the two key passages and canproject simultaneously into both key passages. Another advantageousreduction of the number of component parts is attained when theoperation member is configured simultaneously as an interlocking member.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the annexed drawings, discloses preferredembodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings which form a part of this disclosure:

FIGS. 1A to 1C are side elevational views in section of a safety switchaccording to a first embodiment of the present invention, with the keyintroduced to different degrees; and

FIGS. 2A to 2C are side elevational views in section of a safety switchaccording to a second embodiment of the present invention with the keyintroduced to different degrees; and

FIG. 3 is a top plan view of the key of FIGS. 2A to 2C.

DETAILED DESCRIPTION OF THE INVENTION

In the first embodiment of the safety switch of the present invention,the switch housing 1 of the working mechanism shown in the drawing has afirst key passage 3 extending longitudinally through the switch housing.An additional or second key passage 5 is provided in the workingmechanism of switch housing 1, and extends perpendicularly to first keypassage 3. A key 7 can be introduced from the exterior into either oneof the two key passages 3 or 5, as desired. A plate cam 9 is mountedrotatably within the working mechanism of switch housing 1. The platecam rotary axis 11 extends perpendicular both to first key passage 3 andto second key passage 5. Plate cam 9 projects into both key passages 3and 5.

At a point lying in the intersecting area of the two key passages 3 and5 when the key is not introduced therein, plate cam 9 has a short groove13 extending radially outwardly on each side. Key 7 is configured with afork-like end so as to be introduced into a key passage 3 or 5. On theexterior of each of the two ends of key 7, a partial crossbar 7' isprovided. With the introduction of key 7 into one of the two keypassages 3 or 5, the partial cross bar engages in one of the grooves 13,and thereby carries plate cam 9 along with it in the direction ofcontinued introduction of key 7. This results in a rotary displacementof plate cam 9.

A punch (not shown) engages slidably in a longitudinal direction in theswitch housing. At the other end of this punch, a switch is provided inswitch housing 1, which is likewise not shown. With rotary displacementof plate cam 9 caused by introduction of key 7, the plate cam thruststhe punch and thus proactively operates the switch.

On each of the two sides of plate cam 9, in the area of rotary axis 11,an oval material part 15 is shaped on the plate cam. Each of the twoidentically configured material parts 15 has a groove-like first recess17 arranged opposite and radially facing groove 13 in relation to rotaryaxis 11, as well as two more likewise groove-like recesses 19 offset by90° from first recess 17. The additional recesses 19 are located at thetwo pointed ends of oval material part 15, while first recess 17 isprovided on one longitudinal side.

An interlocking member 21, is provided, in turn, on each side of platecam 9 in addition to the material parts 15 of the plate cam, and extendsin an axial direction. Each interlocking member 21 has an oblong-shapedopening 23 surrounding rotary axis 11. By means of guides in the switchhousing, but not shown in the drawing, the single possible direction ofdisplacement of interlocking member 21 is determined. That direction isperpendicular to rotary axis 11, and at the same time is in thedirection of oblong-shaped opening 23. This direction of displacement isaligned with the intersecting point of the two key passages 3 and 5, andextends along a line bisecting the angles of the two passages.

In other words, that displacement direction is offset 45° from the twokey passages. An end 21' of interlocking member 21 is aligned on thisintersecting point. At the other end more distance from thisintersecting point, interlocking member 21 is supported by means of aspring, not shown in the drawing, mounted on switch housing 1. On theside closer to the plate cam 9, interlocking member 21 has an elevatedlocking tooth or ratchet 25. Ratchet 25 can engage form-fitting both infirst recess 17 and also in the other recesses 19 of material part 15 ofplate cam 9. The possible degrees of engagement in the case of the otherrecesses 19 are thus smaller than with first recess 17. The end 21'aligned on the intersecting point of key passages 3 and 5 projects intoboth first key passage 3 and second key passage 5. This end 21' ofinterlocking member 21, while serving simultaneously as an operatingmember, is configured as a ramp for key 7.

When key 7 is located exterior to key passages 3 and 5, plate cam 9 isaligned such that groove 13 is at the intersecting point of key passages3 and 5. Because of the spring force loading interlocking member 21,interlocking member 21 engages rotary axis 11 at the end ofoblong-shaped opening 23 further away from the point of the passageintersection. Simultaneously, locking tooth 25 engages in recess 17 ofmaterial part 15.

When key 7 is introduced into one of the two key passages 3 or 5, thekey initially strikes against end 21' of interlocking member 21 servingas a ramp for the key. This striking forces interlocking member 21 backcounter to the spring force, in other words out of key passage 3 and 5.Simultaneously, locking tooth 25 is released from first recess 17. Withfurther introduction of key 7, its partial crossbars 71, each of whichis turn engages a groove 13, also displace plate cam 9. Simultaneously,material part 15 continues its movement with its periphery engaginglocking tooth 25. Because of the eccentricity of material part 15,interlocking member 21 is displaced even further out of key passage 3 or5 than key 7 has the capacity to displace the interlocking member.

When key 7 is introduced completely, in other words shortly beforepartial cross bars 7' would again be displaced from grooves 13, lockingtooth 25 drops into one of the other recesses 19. Plate cam 9 is thussecured in this position. The spring bias effecting interlocking member21 is sufficient to hold locking tooth 25 in the other recess 19 evenduring vibration movements. The safety switch of the present inventioncan be configured so that, starting with the plate cam in the securedposition, key 7 can be introduced further into key passage 3 or 5 in thesort of track alignment arrangement, and partial crossbars 7' then leavegrooves 13 once again.

With the removal of key 7, the force exerted through plate cam 9 by itsmaterial part 15 on locking tooth 25 becomes so intensive that lockingtooth 25 is pressed out of the other recess 19. This action frees plate9 for rotary displacement.

In the second exemplary embodiments of the safety switch of the presentinvention, a switch housing 101 is likewise provided with a key passage105. A longitudinally slotted, fork-like key 107 can be introduced intokey passage 105. A plate cam 109 which projects into key passage 105 isrotated with introduction of key 107 in such a manner that partialcrossbars 107' of key 107 engage in grooves 113, which are provided onboth sides of plate cam 109. A material part 115 is shaped around therotary axis 111 of plate cam 109, and is integral with plate cam 109.Part 115 is shaped with a flank 117.

Directly adjacent to each material part 115, an interlocking member 121is provided. Interlocking member 121 has an oblong-shaped opening 123surrounding the rotary axis 111, as is illustrated only in FIG. 2A.Interlocking member 121 is movable perpendicular to key passage 105, andis supported by means of a spring not shown. A locking tooth 125provided on the interior of interlocking member 121 engages on the flankpart 117 of material part 115, when key 107 is located exterior to keypassage 105.

Around the border or periphery of plate cam 109, groove-like recesses119 are provided on both sides. Recesses 119 extend perpendicular to theradial direction and open at one end on the periphery of plate cam 109.With rotation of plate cam 109, this border or peripheral area can reachinto key passage 105.

When key 107 is introduced into key passage 105, the point of the keypresses or forces interlocking member 121 back counter to the bias ofits spring, whereby locking tooth 125 is then released from flank 117.Partial crossbars 107' of key 107 carry along plate cam 109 bydisplacing it until partial crossbars 107' are located behind plate cam109, as viewed from the direction of introduction. Plate cam 109 moves apunch device as indicated in FIG. 2A, which in turn operates the switch.In the arrangement in which partial cross bars 107' are located to therear of plate cam 109, the groove-like recesses 119 are aligned alongkey passage 105, as shown in FIG. 2C. Key 7 can then be introducedfurther into key passage 105 by means of a sort of a track alignmentarrangement, whereby recessed cutout sections 127 provided on theinterior of key 107 engage in the groove-like recesses 119 to secureplate cam 109.

While various embodiments have been chosen to illustrate the invention,it will be understood by those skilled in the art that various changesand modifications can be made therein without departing from the scopeof the invention as defined in the appended claims.

What is claimed is:
 1. A safety switch, comprising:a switch housing: afirst key passage in said switch housing; a key receivable in said keypassage from a location exterior of said switch housing; a plate camprojecting into said key passage and rotable in said switch housingabout a rotational axis upon introduction of said key; and securingmeans in said switch housing for securing said plate cam againstrotation when said key is completely introduced into said key passage,and for allowing said key to be introduced deeper into said key passageafter said plate cam is secured by said securing means.
 2. A safetyswitch according to claim 1 whereinsaid securing means secures saidplate cam when said key is not introduced into said switch housing.
 3. Asafety switch according to claim 1 whereinsaid securing means comprisesat least one recess and a cooperating blocking element movable relativeto said plate cam.
 4. A safety switch according to claim 3 whereinsaidblocking element is movable in a radial direction relative to saidrotational axis, and is spring biased against said plate cam.
 5. Asafety switch according to claim 4 whereinsaid at least one recess isprovided in one side of a shaped material part on said plate cam; and aninterlocking member is arranged on one side of said plate cam andincludes said blocking element.
 6. A safety switch according to claim 5whereinsaid interlocking member comprises an oblong-shaped openingsurrounding said rotational axis of said cam plate.
 7. A safety switchaccording to claim 6 whereinsaid interlocking member is movableperpendicular to said rotational axis of said plate cam.
 8. A safetyswitch according to claim 3 whereinsaid at least one recess is providedin one side of a shaped material part on said plate cam; and aninterlocking member is arranged on one side of said plate cam andincludes said blocking element.
 9. A safety switch according to claim 8whereinsaid interlocking member comprises an oblong-shaped openingsurrounding said rotational axis of said cam plate.
 10. A safety switchaccording to claim 9 whereinsaid interlocking member is movableperpendicular to said rotational axis of said plate cam.
 11. A safetyswitch according to claim 3 whereinsaid at least one recess is providedin an area of said plate cam projecting into said key passage duringrotation of said plate cam; and said blocking element is provided onsaid key.
 12. A safety switch according to claim 11 whereinsaid at leastone recess is configured as a groove; and said key is fork-shaped with alongitudinal slot, said blocking element being formed by recessedcut-out sections on an interior of said longitudinal slot.
 13. A safetyswitch according to claim 1 whereinsaid securing means are symmetricallyprovided on both sides of said plate cam.
 14. A safety switch accordingto claim 1 whereina second key passage extends in said switch housingnon-parallel to said first key passage; and an operation member ismovable along an angle bisecting said first and second key passages, andprojects into said first and second key passages when said key is notintroduced into one of said key passages.
 15. A safety switch accordingto claim 14 wherein said operation member is part of an interlockingmember.